Combined Cycle HRSG and Balance of Plant - Program 88

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1 Combined Cycle HRSG and Balance of Plant - Program 88 Program Description Program Overview The design of modern heat recovery steam generators (HRSGs) and balance-of-plant (BOP) systems is a complex interrelationship between many parameters and variables. HRSGs pose a unique set of operational challenges, due in part to their rapid startup capabilities, high operating efficiencies, multi-pressure circuits, reheat, once-through, combined drum/once-through systems, and numerous varieties available in the basic design. Preventing HRSG tube failures (HTFs) is a priority, but complex failure paths, which are influenced by cycle chemistry or thermal transients, are difficult to understand and mitigate. Limited access and other complexities make inspection and repair of HRSGs very difficult. For 2013, EPRI staff consulted with its members to make several strategic changes that will broaden EPRI s focus on natural gas simple-cycle (SC) and combined-cycle (CC) plants. The members provided valuable feedback on key natural gas generation issues with emphasis on their current and future SC and CC portfolios, and on how EPRI can more fully respond to these specific issues and future research and development (R&D) opportunities. The changes are to consolidate three existing programs (P79, P80, and P88) into two programs structured as a coordinated and complementary set to address all aspects of gas turbine (GT) and CC research areas. The new program titles are: Combined Cycle Turbomachinery (P79) Combined Cycle Heat Recovery Steam Generator (HRSG) and Balance of Plant (P88) The Electric Power Research Institute s (EPRI s) 2013 Combined Cycle HRSG and BOP program (Program 88) provides a complete set of technical tools to improve the performance and reliability of combined-cycle HRSGs and BOP equipment. The program includes a background of HRSG design and development particularly over the last 10 years where HRSG designs have become remarkably complex, operating at significantly higher pressures and temperatures. It provides a comprehensive understanding of available designs and tools for preparing procurement specifications for both new and used HRSG and BOP components based on past research. Research Value Projects include unit-specific and pressure-circuit-specific chemical treatment methods and limits, optimal approaches to preventing HRSG tube failure, and methods for life assessment, nondestructive evaluation (NDE) options, welding, and other repair methods. Using the R&D from this program, members can: Achieve tube failure rates consistent with their risk tolerance and financial models Increase reliability through better understanding of thermal transients Increase understanding and control of flow-accelerated corrosion (FAC) through an initial predictive code and other technologies Optimize HRSG operational and shutdown chemistry through better understanding of the chemistry cycle Identify and correct cycling and thermal transient problems through chemistry cycle guidelines and methods Optimize HRSG inspection and repair by using new hardware, NDE guidelines, and techniques for improving access Establish inspection routines and life assessments of major components p. 1

2 Approach The program portfolio has two primary technical objectives: Provide a holistic approach and perspective on all R&D elements related to integrating all the equipment and systems of a CC HRSG Address all aspects of managing CC HRSG and balance-of-plant assets including life assessment/risk management, O&M improvements, and technology advancements Specific technical interaction and allocation of resources between P88 and other appropriate programs such as Boiler Life and Availability (P63), and Combined Cycle Turbomachinery (P79), etc. will be defined and implemented as required to effectively utilize existing EPRI technical expertise and resources without duplication between programs. Program members receive: Operator guidelines that help monitor, identify, and minimize the effects of shutdown, startup, and thermal transients on fatigue life, while a diagnostic expert system helps control and maintain optimal chemistry. Regional workshops covering HRSG tube failure, cycle chemistry, inspection, and FAC that effectively transfer the knowledge gained through this program. Information on life assessment and risk management topics including damage detection, root cause and solutions, and monitoring and life-predicting analyses HRSG tube failures and life-assessment research, which is continuing to develop a comprehensive methodology to assess cycling capability, including optimizing startup in terms of thermal transients. The program also continues to document case studies and develop life-assessment tools and methodologies HRSG NDE and repair R&D, which includes developing and demonstrating external inspection techniques with remote capability, developing final equipment for HRSG tube elbow replacement near headers, and assessing an internal coating technology to provide protection against FAC. Information on O&M improvements topics including component durability and damage tracking, and repair and refurbishment guidelines Technology advancements topics include engineering and economic assessments, statistics of current HRSG and balance-of-plant Reliability, Availability and Maintenance (RAM) performance, and new and advanced equipments offerings and capabilities. Program additions in 2013 include a greater emphasis on CC plant-wide topics. An online survey will capture the interests, comments and feedback of the program members relating to the potential products, and the feedback from the survey could lead to additional potential products in the 2013 program activities. The EPRI staff and the P88 advisors have identified modifications and additions for transition to This initial planning is part of a major five-year R&D plan for the new CC programs (P79 and P88). The EPRI staff and the P88 advisors are to explore activities, projects, and products for 2013 that will be presented and prioritized at the 2012 fourth-quarter Generation advisory council meeting. The number of products completed in 2013 will be based on the yearly funding levels, coupled with member prioritization provided during each year s third-quarter Generation advisory council meeting. Accomplishments EPRI s thermal transient and cycle chemistry guidelines provide quantitative, specific suggestions for obtaining the best possible performance from existing HRSGs. The guidelines also provide guidance applicable to new units for appropriate design of pressure parts. EPRI has developed comprehensive guidelines on cycle chemistry for all HRSGs, including shutdown/startup chemistry and chemical cleaning. Combined Cycle HRSG and Balance of Plant - Program 88 p. 2

3 EPRI has developed a complete approach to identifying reasons for thermal transients, as well as related analytical tools. EPRI has developed a troubleshooting guide that, through a group of 57 questions, can help identify whether and which underlying causes (or both) of thermal transients are present in the operating practices or in the design of the HRSG. Unique repair technology has been developed, as well as a revision to the interim NDE guidelines, to include case studies of visual techniques and technology transfer materials. Current Year Activities Program R&D for 2013 will continue to focus on thermal transients and chemistry directly responsible for damage to HRSG pressure parts. The scope of the program is expanding to address end-of-life issues to the major components of the HRSG and incorporate balance-of-plant equipment. Specific efforts will include: Exploration of technologies to address HRSG tube failures (HTFs) Technology to assess control of steamside deposition Case studies and development of HRSG life-assessment tools and methodologies Further development and demonstration of remote capabilities for external inspection techniques Exploration of technology for organics treatment Investigation of flexible operation short- and long-term effects Estimated 2013 Program Funding $2.5M Program Manager Bill Carson, , bcarson@epri.com Summary of Projects Project Number Project Title Description P HRSG Reliability This project R&D helps reduce HRSG tube failures by providing guidelines to improve cycle chemistry and thermal transients through management of key failure mechanisms. P Life Assessment/Risk Management P Operations and Maintenance Improvements P Technology Advancements This project provides in-depth investigations and guidelines, addressing high-risk component failure root-cause mechanisms. Corrective solutions and damage mitigation techniques are developed, evaluated, and demonstrated. This project develops technologies and techniques to improve HRSG and BOP availability through enhancement of personnel skills, personnel safety, technology implementation, and automation of information systems. Members can use this project's deliverable products by incorporating the assessments and data into their decision-making for technology selection and procurement. If this information is utilized early in the project development process, substantial benefits can be realized for the overall availability and reliability of the unit. Combined Cycle HRSG and Balance of Plant - Program 88 p. 3

4 P HRSG Reliability (073443) Key Research Question HRSG tube failures are brought about by issues involving thermal transients and cycle chemistry. EPRI s suite of guidelines on HRSG tube failures and cycle chemistry are designed to manage all of these failure mechanisms. Program 88 has completed a series of projects with reports on thermal transient and cycle chemistry issues. As gas begins to take on a bigger role in the generation of electricity, maintaining and improving HRSG reliability becomes more important. The project R&D for 2013 aims to support these goals. Approach Projects include unit-specific and pressure-circuit-specific chemical treatment methods and limits, optimal approaches to preventing HRSG tube failure, and methods for life assessment, nondestructive evaluation (NDE) options, welding, and other repair methods. Using the R&D from this program, members can: Achieve tube failure rates consistent with their risk tolerance and financial models Increase reliability through better understanding of thermal transients Increase understanding and control of flow-accelerated corrosion (FAC) through an initial predictive code and other technologies Optimize HRSG operational and shutdown chemistry through better understanding of the chemistry cycle Identify and correct cycling and thermal transient problems through chemistry cycle guidelines and methods Optimize HRSG inspection and repair by using new hardware, NDE guidelines, and techniques for improving access Establish inspection routines and life-assessments of major components Impact Significant reduction and improved management of chemistry-thermal related generation losses in HRSGs Improved unit availability and reduced O&M costs through prevention of chemically and thermally influenced HTF Control of corrosion damage and deposition problems in HRSGs Control HRSG tube failures to an corporative acceptable level How to Apply Results Members can benchmark their tube failure and chemistry programs independently or in collaboration with EPRI staff to identify areas of deficiency and determine approximate costs. The content of the guidelines then can be used to identify specific actions needed to address those deficiencies in a manner consistent with individual unit characteristics. For example, the chemistry guidelines can be consulted to verify proper selection and optimization of HRSG water chemistry used in individual fossil units. The benchmarking process should be repeated periodically as a means of checking the overall effect of improvements implemented. Success can be gauged by measuring progress against a rigorous set of performance metrics consistent with the EPRI guidelines Products Guidelines for Cycle Chemistry for HRSGs: This report will update the current cycle chemistry guidelines, incorporating additional technology from both EPRI and outside research. The report will describe the organization and activities necessary to implement a successful cycle chemistry program. It has been proven that both single- and two-phase FAC in HRSG plants can be minimized by optimal cycle chemistry. Report Combined Cycle HRSG and Balance of Plant - Program 88 p. 4

5 Chemical Cleaning Guideline: Excessive deposits insulate the underlying area of the HRSG tube and raise the operating temperature of the metal. Porous deposits can act as a concentrating mechanism for the boiler water treatment chemicals and can lead to excessive corrosion and caustic gouging. Removal of the deposits has advantages other than minimization of failures. Cleaning reveals the true boiler metal condition, allowing more complete inspection. A clean unit will operate more efficiently as well. This update is expected to include new technology and procedures for when and how to successfully clean the HRSG. P Life Assessment/Risk Management (073444) Key Research Question The underlying driver for component condition assessment is the need to manage component life to achieve plant safety, reliability, and economic objectives. Recent changes in the power industry have heightened the importance of these objectives, especially costs, and in many instances have renewed interest in comprehensive condition assessment and condition monitoring. Knowledge of component condition and expected remaining life is critical to successfully extending major maintenance outage intervals and to managing generating units dedicated to load following, twoshifting, and other cycling modes. The large number of startups and rapid load changes that cycling entails adds substantial thermal stress to many boiler components and makes water chemistry more difficult to control, promoting corrosion and other material degradation phenomena. These conditions can translate into greater risk of component failure. Similarly, rapid load changes and cyclic operation can exacerbate certain damage mechanisms, such as fatigue and corrosion. For many plants, maintenance challenges are greater at a time when staff and budgets have been reduced, forcing them to "do more with less." Reliable condition assessments are crucial for managing units dedicated to load-following, two-shifting, and other cycling modes. Knowledge of component condition and expected remaining life is similarly critical to success when efforts are made to extend major maintenance outage intervals to reduce costs and improve availability. Approach This project will begin development of a predictive methodology for HRSG component life assessment. Work will continue on development and validation of research on HRSG pressure-part, thermal transient limits, and mitigation. Research will be able to factor in how the operation of the unit affects the life calculation, inspections, and testing requirements. This work also is being extended to the balance of combinedcycle plant components. Impact Achieve significant improvement in combined-cycle plants, including the HRSG and balance-of-plant availability Reduce operations and maintenance cost through reduced component failure throughout the combinedcycle HRSG and BOP How to Apply Results The end-of-life methodology can help combinedcycle HRSG and BOP owners/operators determine when inspections should occur, what types of inspection/testing are needed, and how to plan for replacement or repairs. The approach will take into account the previous years' work on thermal transient, cycling, and design issues. Combined Cycle HRSG and Balance of Plant - Program 88 p. 5

6 2013 Products Document Formalized Plans for Life-Management Guide to Include Tubes and Larger Components: With the HRSG fleet aging, a proactive approach needs to be taken for life management. This project will draw on information and technology already developed and apply it to the HRSG fleet. Inspection Guideline for Life-Assessments of a Combined Cycle HRSG and BOP equipment: As the HRSG fleet ages, a process is needed to determine when to inspect, what to inspect, and how often to stay out in front of an availability loss. This project can help assess the damage mechanisms before they become detrimental to the availability of the units. P Operations and Maintenance Improvements (073445) Key Research Question Research in new maintenance strategies will become increasingly important to EPRI members as they continue to look for ways to reduce costs while maintaining high availability. This project is expected to help members stay focused on both existing and emerging technologies while understanding the impact that these technologies have on plant operation and maintenance Approach Typically, the costs of the labor and the materials necessary to keep a power plant's equipment in good operating condition increase as the equipment ages. With time, the equipment can become less reliable and have higher maintenance costs. This project addresses these core issues facing plant staff today Impact Enhance unit availability Improve O&M activities through peer-to-peer involvement, lessons learned, experience, and industry best practices Reduce tube/header examination and repair times Experience fewer HTFs through improved operation and maintenance activities Validate damage assessment and models How to Apply Results The documents produced and PM modules added to the PM Basis database can be used when a utility is faced with equipment repair or testing or component condition assessment. Members can integrate the content in these guidelines in their own procedures and training materials. The guidelines can be placed on internal networks and provide an excellent resource for continuous improvement training, as well as new-hire orientation for system owners and maintenance staff. Utilities planning new equipment purchases can take advantage of the guidelines' content in preparing their own site-specific procurement specifications 2013 Products Plant Maintenance Basis Database: Program 88 will join with EPRIs Generation Maintenance Applications Center (GenMAC) program (Program 104) to include PM Basis with the suite of tools available for members to improve the reliability of the HRSG and BOP equipment. Resource Combined Cycle HRSG and Balance of Plant - Program 88 p. 6

7 Continuation of "Snake Robot" technology: Install NDE and inspection techniques to the platform to offer members additional capabilities during outages. GTCC O&M Cost Analyzer: Excel spreadsheet-based software estimates the O&M costs for simple-cycle and combined-cycle plants for user-specified operating scenarios. Gas turbine model-specific costs are based on component replacement and repair costs, life estimates, and maintenance intervals. A probability analysis feature incorporating industry experience data allows the user to examine the impact of unplanned maintenance events. This product is shared with EPRI s Combined Cycle Turbomachinery program (Program 79). Hardware Software P Technology Advancements (073446) Key Research Question Nearly 237 gigawatts of natural gas-fired generation was added between 2000 and This quantity represents about 81% of all generation capacity added over that period. Most of this capacity is in the form of combined-cycle plants, and about 65% of current natural gas generation capacity launched since 1980 used combined-cycle units. This trend is expected to continue as the need to replace older coal-fired generation is dominated by expected low natural gas prices and the shorter construction times and lower capital costs for gas-fired generation. Approach Optimization of a HRSG and BOP design is more than just maximizing thermal efficiency for a single performance point. HRSG development has introduced many new advances not previously available to plant developers as systems become more complex with higher temperatures and pressures. HRSGs have increasingly been operated in cyclical mode, and less often in baseload, even as high-efficiency, three-pressurereheat units become standard. There is a need to better understand and design for the new technology advancements. Impact Improve unit availability significantly Reduce operations and maintenance costs via technology incorporated into new builds that allow for an increased awareness of the thermal and chemistry factors contributing to HRSG tube failure as well as effective inspection and repair techniques How to Apply Results Some of the latest advances in HRSG design include improved tubing materials, advancements in once-through technology, improved "constructability" concepts, automated manufacturing processes, improved thermal expansion capabilities, improved fin attachment processes, enhanced HRSG internals access, improved exhaust flow routing, and improved tube bundle manufacturing processes. This project looks to improve on the technologies already available and establish HRSGs and BOP equipment able to meet the demands required by the new operating environment. Combined Cycle HRSG and Balance of Plant - Program 88 p. 7

8 2013 Products New HRSG Procurement Guidelines: This project would be an update to the existing HRSG procurement guidelines, incorporating thermal transient projects produced in Program 88 over recent years. Combined Cycle Environmental Control Technology Handbook: Report update assesses advancements in equipment and systems for emissions controls and provides technical guidance for regulatory issues affecting plant siting. Typical regional permit levels for priority pollutants are included. Trends in new regulatory requirements are discussed (shared with P79). Future Year Products Repowering Existing Fossil Plants with Gas Turbines and HRSGs: There is a growing trend in the utility industry to convert existing coal-fired power plants to burn what are, by some, considered to be more environmentally-friendly fuel types, such as biomass and natural gas. This trend is driven by a number of factors, including state-level renewable portfolio standards; federal incentives and looming environmental regulations; consumer demand and environmental awareness; and an economic climate that is making coal less attractive. Although conversion costs can be expensive, utilities already have the facilities sited and water supply and transmission lines established. Converting existing facilities can often cost less than installing the emissions control systems required to keep an antiquated coal plant running. This project would help to establish best practices and provide guidance to ensure reliable HRSG and BOP components. 12/31/14 Combined Cycle HRSG and Balance of Plant - Program 88 p. 8

9 Supplemental Projects SCR Catalyst Replacement Options for Gas Turbine/Combined Cycles (072057) Background, Objectives, and New Learnings Selective catalytic reduction (SCR) technology for controlling nitrogen oxides (NOx) is broadly applied to natural gas-fired combustion turbines, operating in combined cycle. The SCR performance depends on numerous design and operating variables, including catalyst activity (K). Ideally the SCR could run for an indefinite period of time; however, factors such as trace metal deposition will cause the catalyst to deactivate. A catalyst is considered to be at end-of-life when the required NO removal cannot be achieved, or can be achieved only with significant residual NH 3 (ammonia slip). The widespread industry commitment to SCR technology is now reaching a level of maturity, where catalyst is reaching the end-of-life, and plants are now considering options to add, replace, or regenerate catalyst. This project evaluates the least-cost way of maintaining the NO-removal capabilities of SCR systems, as installed in natural-gas-fired combustion turbines operating in combined cycle. In the context of this discussion, the NO-removal capabilities are the control of NO, without excessive ammonia slip, for a minimal gas pressure drop. The knowledge developed by this project will assist in understanding the gas turbine emission control system configurations(s) and fine-tune the EPRI research specific to current best practices, vendor capabilities, and SCR catalyst system design improvements. Project Approach and Summary The approach in this project is to evaluate the cost and performance of three catalyst management options. Cost and performance data will be solicited from catalyst suppliers and regenerators. Notably, only new catalyst is considered commercially proven. The two major providers of regeneration services have never commercially regenerated catalyst for natural-gas-fired combustion turbines. Although one catalyst supplier offers an ammonia destruction catalyst, experience is limited to one, small combined-cycle unit. Performance has not been thoroughly documented. Consequently, there is uncertainly in these approaches. A host site or sites for an engineering and risk assessment of these options will be defined. The details of the SCR design combustion turbine process conditions, specifics of the HRSG will be established, as well as the geometric details and activity of the catalyst. Benefits The results will assist gas turbine owners and operators in their investigation into the selection of SCR catalyst system design alternatives and will directly benefit the public because it lowers environmental emission levels and future risks of a power interruption or power outage due poorly functioning emission control technologies. Combined Cycle HRSG and Balance of Plant - Program 88 p. 9

10 Catalyst Regeneration for Gas Turbine and Combined Cycle SCRs (073447) Background, Objectives, and New Learnings Selective catalytic reduction (SCR) technology for controlling nitrogen oxides (NOx) is broadly applied to natural gas-fired combustion turbines, operating in combined cycles. The use of SCR NOx control is the state of art on all new and many existing natural gas-fired combined cycle generating facilities. Further, the required control of NOx is becoming increasingly more stringent, to as low as 2-3 ppm (at 15% oxygen content). Several factors affect the performance of the SCR system in meeting low outlet levels of both NOx and the residual NH 3. The effective mixing of ammonia reagent in flue gas is key to deliver a uniform distribution of NH 3 and NOx. Equally important is the condition of the catalyst; specifically, the activity for reacting NOx with NH 3. Ideally, the SCR could run for an indefinite period of time; however, factors such as trace metal deposition can cause the catalyst to deactivate over time, requiring periodic change outs. Historically, new catalyst has been used. SCR systems now are reaching an age at which significant investment must be made to address the issue of catalyst deactivation. Rather than replacing the catalyst with new, catalyst regeneration is being offered as an option, offering substantial savings. However, at present, there is no experience with regenerated catalyst in a combined-cycle utility power generation environment Project Approach and Summary This project will evaluate the efficacy of using regenerated catalyst in place of new material in combined-cycle combustion turbine application. Two complete modules of spent catalyst were obtained from Consolidated Edison s East River Unit 10. The spent catalyst was characterized in a series of laboratory tests, and regenerated by the two leading providers of this service. The two test modules have been re-installed in Unit 20 and will be operated for four years. Samples of the regenerated catalyst will be obtained annually, and tested for NOx activity, SO 2 conversion, and surface chemical and physical characteristics, providing insight as to useful life. Although this is a four-year project, a significant amount of the information will be available within the first year. Benefits Regenerated catalyst in combustion turbine applications could offer substantial savings over the purchase of new catalyst. Regeneration can be economically attractive if the performance with respect to NOx reduction, NH 3 slip, and deactivation rates is similar or better to that of new catalyst. As an example, for a 500-MW combined cycle unit featuring 130 m 3 of catalyst, the market price for new replacement catalyst can approach $1M. A savings of $0.5M is possible by using regenerated material. This project will provide experience with regenerated catalyst, and thus improve access to lowcost replacement catalyst for SCR process equipment. Combined Cycle HRSG and Balance of Plant - Program 88 p. 10